1. Field of the Invention
This invention relates to a cable clamp for holding cables in communication equipment and electronic equipment, and more particularly to a cable clamp suitable for clamping very fine cables.
2. Description of the Related Art
Recently, an increase in channel capacity is being demanded of communication equipment and electronic equipment. Further, the thickness of transmission cables installed in the equipment has been decreased according to the progress of manufacturing techniques. Particularly, in the communication equipment, to provide a high-speed and stable communication quality, optical transmission using optical fiber cables has been becoming dominant. In an optical communication unit, an optical fiber cable is clamped within the unit and an extra length of the cable is bunched. To carry out such treatment on optical fiber cables, cable clamps are used.
FIGS. 4A, 4B, and 4C are diagrams showing examples of conventional cable clamps for treating cables of a general type, wherein FIG. 4A shows an M clamp; FIG. 4B shows an openable clamp, and FIG. 4C shows a twist clamp.
The M clamp 101 shown in FIG. 4A has an open central portion, and downward sloping portions extend from opposite sides so as to provide a guide for cables 100 as they are pushed in through the open central portion. The M clamp 101 has a means for having itself fixed to a chassis or a printed wiring board. The cables 100 are inserted into the M clamp 101 to be held therein, by being pushed in through the central open portion.
The openable clamp 102 shown in FIG. 4B has an opening and closing mechanism a top of which is openable. The cables 100 are caused to be received in the clamp 102 by opening the opening and closing mechanism, and are held therein by closing the opening and closing mechanism thereafter.
The twist clamp 103 shown in FIG. 4C is in the form of a string having retaining portions at opposite ends thereof. The cables 100 are received and wound by the clamp 103 which is set open in advance, and thereafter the clamp 103 is twisted, whereby the cables 100 are tied together and held in the clamp 103.
FIG. 5 is a perspective view showing an example of the arrangement of an optical communication unit using conventional cable clamps. FIGS. 6A and 6B are perspective views useful in explaining how the optical fiber cables are treated using the above-described conventional openable clamp, wherein FIG. 6A shows an open state of the opening and closing mechanism, and FIG. 6B shows a closed state of the same.
In the case of the optical communication unit shown in FIG. 5, the openable clamps 102 shown in FIG. 4B are used. The clamps 102 are fixedly arranged at respective predetermined locations on the printed wiring board 104, etc. within the optical communication unit, and a clamping treatment and an extra length-bunching treatment are carried out on the optical fiber cables 105 introduced into the clamps 102.
The clamping treatment and the extra length-bunching treatment are carried out by receiving the cables 105 into the opening and closing mechanism in the open state as shown in FIG. 6A and then closing the same, as shown in FIG. 6B.
Further, there has also been proposed a cable clamp particularly suitable for treating flat cables (see e.g. Japanese Unexamined Patent Publication No. 2002-262441). This cable clamp is comprised of sandwiching boards for sandwiching the flat cable and a guide bar, and holds the cable by sandwiching the cable between the sandwiching boards and rotating the cable and the boards. In the case of this cable clamp, the cable is clamped by applying an external pressure thereto to press it down for retainment.
However, the above-described conventional cable clamp is not very suitable for treating the optical fiber cables. More specifically, the optical fiber cables having come into wide use for attaining very high speed transmission and very large channel capacity communication so as to cope with the broadband era have become very fine, that is, the diameter thereof has been changed e.g. from 0.9 mm or 0.4 mm to 0.25 mm. Some cables having very small diameters as described above are very nearly transparent, and difficult to visually recognize just as in the case of fishing lines. They tend to be entwined, caught, or sandwiched during the clamping or extra length-bunching treatment, which makes it very difficult to work on them and makes the cables easy to be broken. When such very fine cables are treated by the conventional cable clamps, they are liable to come off or extend off from the clamps, and are also liable to be broken.
For example, in the M clamp having an open central portion, cables received therein are liable to come off from the open portion. When cables come off from the clamp, they are caught within the apparatus, which can cause breakage thereof. The openable clamp has a lock structure for locking cables by the opening and closing mechanism thereof, and hence cables tend to be caught by a hook or extend off, as shown in FIGS. 6A and 6B, which causes breakage of the cables, similarly to the M clamp. The breakage of cables is liable to occur especially when cables are wound a plurality of times by the extra length-bunching treatment into a loop. Further, workability is low, and when a long cable is treated, the cable is required to be wound a larger number of times by the extra length-bunching treatment, which makes the winding operation troublesome. In the twist clamp which is twisted after receiving cables, workability of the clamp is low especially when fine cables are treated.